Firstly, let me just say how good this game looks. The models of the NPCs, enemies, weapons and armour are painstakingly crafted, and the worlds they are set against are huge, detailed, and bleak. Each of the worlds has its own feel, but there is always an air of oppression; a stark reminder that this is a world in conflict. If you want to show just how good a dungeon crawler can look, this is the game to choose.
The progression system is deep, with plenty of stats to upgrade, and weaponry which can be upgraded along multiple paths, meaning you have to choose between pure physical damage, magic, fire, stat-dependent damage. The upgrades cost souls, which are gained from killing enemies, and weapons require various stones, which occasionally drop from enemies. The scarcity of some of these resources mean that choosing an upgrade becomes an important and sometimes difficult decision.
The combat relies upon knowledge of your weapons, knowledge of the enemies potential attacks, and equipment that complements your play style. Everything affects how your character fights, from the size and weight of your equipment, your stats, the type of weapon, whether you wield two weapons, weapon and shield, or a two handed weapon. The combat seems simple at first, but is a suprisingly deep system, and the blocking, parrying, and dodging abilities give a solid, immersive feeling to the fights, aided by the brutal animations for critical strikes.
Everyone talks about the difficulty of this game, and it's true, this game will relentlessly punish you for every mistake you make. That said, the game is not unfair, and each time you die, you will learn from it, and hopefully not try the same thing that got you killed again. Suprisingly, getting killed is not as frustrating as it sounds. You keep all your items, but lose any souls you had aquired; you will have one chance to get those souls back by finding your bloodstain, however, if you die before finding it, you lose all those souls for good. As souls are required in order to improve your character, this nurtures a healthy respect for a cautious approach in players. Those who run in swinging will die fast. This is not God of War.
Other players can be invited to your game to help, or they can invade in an attempt to kill you in order to ressurect themselves. Player interaction is kept to a minimum quite deliberately. Messages left by other players can only be from a list of set text in order to avoid others giving away very detailed strategies for some enemies, instead restricted to basic hints, or notes on which direction to go, although not all messages can be trusted...
I have played an awful lot of RPGs, from Baldur's Gate to The Elder Scrolls, and for a pure action RPG with an authentic battle system and engrossing world, you can't beat Demon's Souls. You will get obsessed with this game, and if you own a PS3, you owe it to yourself to visit the realms of Boletaria, and try your skill against a truly brutal game.